X-ray ionization yields and energy spectra in liquid argon

Abstract

The main purpose of this work is to provide reference data on X-ray ionization yields and energy spectra in liquid Ar to the studies in the field of Cryogenic Avalanche Detectors (CRADs) for rare-event and other experiments, based on liquid Ar detectors. We present the results of two related researches. First, the X-ray recombination coefficients in the energy range of 10-1000 keV and ionization yields at different electric fields, between 0.6 and 2.3 kV/cm, are determined in liquid Ar based on the results of a dedicated experiment. Second, the energy spectra of pulsed X-rays in liquid Ar in the energy range of 15-40 keV, obtained in given experiments including that with the two-phase CRAD, are interpreted and compared to those calculated using a computer program, to correctly determine the absorbed X-ray energy. The X-ray recombination coefficients and ionization yields have for the first time been presented for liquid Ar in systematic way.KEYWORDS: X-ray recombination coefficients and ionization yields in liquid argon; X-ray energy spectra in liquid argon.

Simulation of argon response and light detection in the DarkSide-50 dual phase TPC

“…when the track is shorter than the mean ionization electron-ion thermalization distance. This is shown by T. H. Joshi et al [30] for 37 Ar in LAr. The Doke-Birks model [24], which is based on Birks' law, empirically parametrizes the recombination effect and was found to be in good agreement with data in the "long" track regime.…”

“…A scaling factor, whose deviation from one is comparable with the inaccuracy in collection efficiency, is expected. Tuning of the recombination probability relies on the simultaneous fit of the energy spectra induced by the decays of 37 Ar, 83m Kr, and 39 Ar (from the atmospheric argon run), which are present or artificially produced and distributed in the active mass. Cosmogenic 37 Ar decays via electron capture, emitting an X-ray of 2.62 keV with 8.4% Branching Ratio (BR).…”

Measurement of the ionization yield of nuclear recoils in liquid argon using a two-phase detector with electroluminescence gap

“…The ionization efficiency is defined as the ratio of the ionization yield of nuclear recoils (Q y,nr ) to that of electron recoils (Q y,ee ), at the same energy: L ion = Q y,nr /Q y,ee . Combining the data of table 1 and the data of ionization yield of electron recoils from [14], one can obtain that L ion amounts to 0.31 ± 0.06 at 0.56 kV/cm and 0.37 ± 0.07 at 0.62 kV/cm. Ionization charge distribution in liquid Ar induced by nuclear recoils due to neutron scattering, obtained from figure 2 using 59.5 keV X-ray line calibration and subtracting background-run and gamma-ray contributions.…”

“…For the latter one should know, in turn, the ionization yields for 59.5 keV X-rays in liquid Ar, i.e. for electron recoils induced by X-ray absorption in liquid Ar; these were deduced from our previous work [14], for given electric fields in liquid Ar.…”

“…The data are extrapolated to the electric field value of 0.56 kV/cm; the result is shown in figure 6. One can see that the remarkable energy dependence is revealed: the ionization yield first decreases [28] (at 0.27 keV, 2.8 keV and 5.9 keV), in Bondar et al [14] (at 35 keV), in Scallettar et al [29] (at 364 keV) and in Shibamura et al [30] (at 976 keV). The spline function fit for the ionization yield is also shown.…”